The sun is incredibly massive object and it causes the space around it to bend. This causes the planets to pulled to the sun or the planets move in an elliptical path around the sun. But I don't understand how the curvature in space can cause the pulling or what cause the planets to move in elliptical path?
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3$\begingroup$ youtube.com/watch?v=DdC0QN6f3G4 $\endgroup$– JoldApr 11, 2013 at 4:21
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$\begingroup$ @elfmotat Very nice! And thank goodness it is not that terrible rubber sheet analogy! Though to my eyes it looked like the straight path of the falling apple was slightly curved. Holding a pen to the screen I saw it was straight, so it must be some kind of optical illusion. Don't know if others are prone to this. $\endgroup$– MichaelApr 11, 2013 at 4:26
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$\begingroup$ Yes. David Z. points to essentially same question. L. Motl answered it very well there. The OP may also want to look at en.wikipedia.org/wiki/Spacetime. $\endgroup$– user12811Apr 11, 2013 at 4:37
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$\begingroup$ @elfmotat: That's very very precise. Good for "no-math" GR introductory ;-) $\endgroup$– Waffle's Crazy PeanutApr 11, 2013 at 4:45
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2$\begingroup$ @annav Voting to close is not just for worthless questions. On the close menu, there is an option to vote to close as a duplicate (or, if you don't have 3000 reputation, to flag as a duplicate), which is what you use when the question is good but just happens to already have been asked. The other close reasons are for when the question needs improvement. Remember, closing is often temporary! $\endgroup$– David ZApr 11, 2013 at 19:29
2 Answers
As this is not closed as a duplicate I will try a simple answer, though the links in comments are adequate.
In Newtonian mechanics one has the planetary bodies which exert a force on each other.
In General Relativity the same planetary bodies distort the space geometry around them, rather than acting on each other.
The force concept is subsumed by the shape in space. If there are no masses then the space is undistorted. One mass distorts the space around it in a calculable way.
Two masses change in concurrence the space such that the trajectory they travel on follows the least resistance path in this distorted space. Calculations show a small deviation from the solution of Newtonian equations and the consequent ellipses, but important enough for satellite paths and navigation. The geometry is still elliptical,except that it is a path through space and not a trajectory at the end of a force field.
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$\begingroup$ Do you disagree that the question should be closed as a duplicate? $\endgroup$– David ZApr 11, 2013 at 15:53
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$\begingroup$ @DavidZaslavsky I agree it is a duplicate. I anwered because it was not being closed :). $\endgroup$– anna vApr 11, 2013 at 16:05
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1$\begingroup$ It was not being closed precisely because people like you didn't vote to close it. ;-) Also, when someone posts an answer to a question, we (moderators) take it as a sign that the answerer thinks the question should remain open. $\endgroup$– David ZApr 11, 2013 at 16:10
Space "geometry"... seems to ignore real cause and effect. See this for another approach: http://metaresearch.org/cosmology/gravity/possiblenewpropertiesofgravity.asp
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$\begingroup$ The linked article displays a lack of comprehension about how general relativity works. the ADM formulation of relativity explicitly shows how the law of cause and effect corresponds to a relativistic spacetime. $\endgroup$ Apr 14, 2013 at 20:47